With the higher speed, the higher capacity, and higher density of electronic circuits, power and currents increase as power voltages decrease, and power distribution is a significant issue in present electronics systems. A current is necessary for a switching transistor circuit to charge load and the current, which is impossible to be supplied from a voltage regulator module (VRM), is supplied by the decoupling capacitor. The decoupling capacitor causes a resonance phenomenon by an equivalent series inductance (ESL) component and the capacity of the capacitor, and acts as an inductance in a region higher than the resonance frequency and causes increase in impedance. The decoupling capacitor is placed as near the semiconductor device as possible for reduction of the ESL.
Further, to realize the lower impedance than that of a surface-mounted capacitor, a study on embedding of a capacitor in a semiconductor package or a board using a thin dielectric material between the power plane and the ground plane has been made (for example, see Non-patent Document 1 (Prathap K. Muthana, Design of high speed package and boards using embedded decoupling capacitors, (U.S.), Georgia Institute of Technology, August, 2007)). In the embedded decoupling capacitor, it is possible to make the wiring distance to the semiconductor device shorter than that of the surface-mounted capacitor.
However, in the embedded decoupling capacitor in related art, for example, as pointed out in Patent Document 2 (JP-A-2005-72311), respective electrodes at both sides with a dielectric layer of the capacitor in between are respectively connected to single electrode terminals, and the magnetic field formed by one current channel is not cancelled and reduced by the magnetic field formed by another near current channel. Thus, the effect of inductance reduction has been limited.
Accordingly, in order to further reduce the ESL, for example, in Patent Document 1 (JP-A-11-45822) and Patent Document 2, a method for setting directions of currents flowing in a pair of electrode plates or electrode layers forming the capacitor as different as possible and a method of parallel-connecting plural capacitor elements each including a pair of capacitative elements to distribute currents into n channels and make an effective inductance to 1/n (one-nth) have been proposed.
Patent Document 3 (JP-A-2007-116178) and Patent Document 4 (JP-A-2007-116179) are also cited.